The present invention relates to a mixer for mixing at least two flows of gas or other Newtonian liquids, with a main flow channel through which the first flow of gas passes, and incorporated surfaces that are arranged therein, these incorporated surfaces affecting the flow, the incorporated surface being a vortex-generating disk that has a leading edge that is oriented against the flow and about which the flow can move freely, the shape of this leading edge having a component that acts in the main direction of flow of the gas, and a component that acts transversely to this.
In order to mix flows of gas or liquids in pipe lines or channels, given a turbulent flow, one requires mixing lengths of 15 to 100-times the diameter of the channel. The length of this mixing section can be reduced significantly by using suitable static mixers in the form of incorporated bodies. However, in most of the systems that are usually used, a major loss of pressure has to be accepted if great demands are to be imposed with respect to homogeneity of the mixture that is produced. Many conventional mixing systems are also restricted to simple geometry, e.g., cylindrical pipes or rectangular channels, and cannot be used over great lengths and in complex mixing-chamber systems.
U.S. Pat. No. 4,527,903 describes a static mixer for use in a cooling tower; in this, the incorporated structures are delta-shaped or circular sheet-metal disks that the flow strikes at an angle; vortices are formed at their leading edges. The stationery and stable vortex systems that are so formed act in the wake of the flow; the components that are to be mixed are rolled up in the form of layers, which results in very rapid mixing with very small pressure losses. These so-called incorporated vortex structures have proved themselves in practice because of the short mixing sections that they make possible.
It is the objective of the present invention to describe a mixer for mixing at least two flows of gas or other Newtonian liquids, which is characterized by rapid mixing in short mixing sections, even if a comparatively small proportion of an additional component is to be mixed in with a volume flow.
This objective has been achieved with a mixer having the features described in the introduction hereto, that is characterized in that the incorporated surface has a chamber into which a separate flow channel for a second flow of gas leads; and in that on the rear side of the incorporated surface that faces away from the inflow of the first gas flow the chamber has outlet openings into the first flow of gas.
The advantages of such a mixer are seen, in particular, in those cases when a relatively small volume flow of the second component is to be mixed into a large volume flow of a first component and, at the same time, homogenization is to be achieved in a short mixing section. The chamber into which the flow channel for the second flow of gas leads makes it possible to distribute the outlet openings for the second flow of gas according to the manner in which the mixer is operated, i.e., these outlet openings can be arranged with a great degree of design freedom. Thus, for example, it is possible to orient the outlet openings against the main flow of gas, or else incorporate baffles that direct the flow of gas that emerges from the outlet openings into the area of the vortexes that are being formed by the leading edges of the disc.
Application possibilities can be seen, for example, in denox plants for scrubbing smoke gases or when processing the dust collected by electro-filters. When scrubbing smoke gas, NH3 or NH4OH is to be mixed into the smoke gas that flows into the reaction chambers, the proportion of ammonia compounds amounting to only about 2%-mass. In this case, using a mixer according to the present invention permits rapid mixing of the two components in a short mixing section. The result of this thorough mixing it is that the profile of the gas and/or liquid flow that it is passed through is evened out, so that performance losses are avoided. Despite the fact that they form extended and stable vortices, the incorporated vortex surfaces cause relatively little resistance to the flow since not all of their surface acts as a baffle; rather, their leading edges generate vortex fields that widen out automatically in the direction of flow, without any additional incorporated structures or baffles being needed to achieve this widening.
A further contribution to achieving homogenization in the shortest possible mixing section is made if, according to a preferred configuration of the present invention, the outlet where the second flow of gas enters the first flow of gas is located in the area of the front half of the disc. In this way, the second flow of gas that is introduced by way of the separate flow channel is picked up by the vortex fields that are generated in the front edge area of the disc.
An additional advantage is that the chamber can be used to reinforce the incorporated surfaces. To this end, it is proposed that the chamber be provided with side walls that are an angle to the disc and stiffen the disc against bending loads and possible oscillations.
With respect to the arrangement of the flow channel for the second flow of gas within the main flow channel, it is proposed that the separate flow channel be led to this on the front side of the disc. In this way, the installed volume of the separate flow channel has no effect on the formation of vortices and their propagation on the rear side of the disc.
Finally, in order to achieve structural unification and thus simplification, it is proposed that the disc be supported in the main flow channel by struts, of which one is in the form of a tube and forms the separate flow channel. In this case, the flow channel assumes an additional static function in the arrangement of the incorporated vortex surfaces within the main flow channel.